Expanding thermal device and system for effecting heat transfer within electronics assemblies

ABSTRACT

Heat transfer devices and systems for thermally coupling electrical components to a heatsink can comprise one or more all-metal heat transfer device(s) thermally coupling at least one electrical component to a heatsink. A heat transfer device can comprise a metal cup attached to a metal heatsink, and a metal piston and a compliant device disposed in the cup. The piston is forcible to a secured first position, upon reflowing solder, while compressing the compliant device. Upon reflowing solder again, the compliant device causes the piston to bias and attach to the electrical component to provide an all-metal thermal path and absorb assembly tolerances to avoid using thermal gap fillers. A method is provided for thermally coupling a heatsink to a plurality of electrical components via a plurality of all-metal, expandable heat transfer devices.

BACKGROUND

Often when assembling electrical circuit boards, thermal gap fillers arerequired in order to absorb assembly tolerances while still maintaininga thermal path from the circuit board to a heatsink for normal operationof the board and its components. During assembly, a large surface areais typically “gap filled” between the electrical chips and a heatsink inorder to transfer heat from the chips. However, gap fillers have a lowthermal conductivity as compared to metal heat transfer devices, forexample. Moreover, the gap filler process can be time consuming andcostly. In addition, the area of the gap fillers on a circuit boardoften become the area of the highest temperatures during operation ofthe chips.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of the invention will be apparent from thedetailed description which follows, taken in conjunction with theaccompanying drawings, which together illustrate, by way of example,features of the invention; and, wherein:

FIG. 1A is a cross-sectional view of a system for transferring heat froman electrical component to a heatsink, in accordance with an example ofthe present invention.

FIG. 1B is a cross-sectional view of the system of FIG. 1A in anexpanded state, in accordance with an example of the present invention.

FIG. 2 is an exploded view of FIGS. 1A and/or 1B, in accordance with anexample of the present invention.

FIG. 3 is a cross-sectional view of an electronics system fortransferring heat from an electrical assembly to a heatsink, inaccordance with an example of the present invention.

FIG. 4 is a cross-sectional view of a system for transferring heat froman electrical component to a heatsink, in accordance with an example ofthe present invention.

FIG. 5 is a cross-sectional view of a system for transferring heat froman electrical component to a heatsink, in accordance with an example ofthe present invention.

FIG. 6A is a cross-sectional view of a system for transferring heat froman electrical component to a heatsink, in accordance with an example ofthe present invention.

FIG. 6B is a cross-sectional view of the system of FIG. 6A in anexpanded state, in accordance with an example of the present invention.

FIG. 7 is an exploded view of a system for transferring heat from anelectrical component to a heatsink, in accordance with an example of thepresent invention.

Reference will now be made to the exemplary embodiments illustrated, andspecific language will be used herein to describe the same. It willnevertheless be understood that no limitation of the scope of theinvention is thereby intended.

DETAILED DESCRIPTION

As used herein, the term “substantially” refers to the complete ornearly complete extent or degree of an action, characteristic, property,state, structure, item, or result. For example, an object that is“substantially” enclosed would mean that the object is either completelyenclosed or nearly completely enclosed. The exact allowable degree ofdeviation from absolute completeness can in some cases depend on thespecific context. However, generally speaking the nearness of completionwill be so as to have the same overall result as if absolute and totalcompletion were obtained. The use of “substantially” is equallyapplicable when used in a negative connotation to refer to the completeor near complete lack of an action, characteristic, property, state,structure, item, or result.

As used herein, “adjacent” refers to the proximity of two structures orelements. Particularly, elements that are identified as being “adjacent”can be either abutting or connected. Such elements can also be near orclose to each other without necessarily contacting each other. The exactdegree of proximity can in some cases depend on the specific context.

An initial overview of technology embodiments is provided below and thenspecific technology embodiments are described in further detail later.This initial summary is intended to aid readers in understanding thetechnology more quickly but is not intended to identify key features oressential features of the technology nor is it intended to limit thescope of the claimed subject matter.

A system for effecting heat transfer within an electronics device bythermally coupling at least one electrical component to a heatsink andabsorbing assembly tolerances, in accordance with one example, isdisclosed. The system can comprise at least one electrical component aspart of an electronics assembly and a heatsink operative to transferheat from the electronics assembly. The heatsink can have a counterboredefining a cavity, or the heatsink may have a planar heat transfersurface. An expanding thermal gap fill heat transfer device can bepositioned in the counterbore (or biased against the heat transfersurface of the heatsink) and thermally attachable to the at least oneelectrical component. The system provides a system of transferring heatfrom a circuit board or other electronics assembly that accounts forassembly tolerances while providing a sufficient thermal path for theheat transfer.

In one example, an expanding thermal gap fill heat transfer device cancomprise a piston moveable within the cavity and a flowable material(e.g., solder) disposed about the piston and/or the cavity. The flowablematerial can comprise a lower melting point than the piston and theheatsink, and the flowable material can be transitional between a solidand liquid state upon the application of energy, such as heat. The heattransfer device can further comprise a compliant device biasing thepiston in a direction towards the at least one electrical component, thecompliant device being deformable, and thus movable from a compressedstate to an expanded state to facilitate movement of the piston. In thisexample, the piston can be held in a first position by the flowablematerial (being in the solid state), the compliant device being in thecompressed state in this first position of the piston. Upon reflowingthe flowable material, the piston can move or be caused to move into asecond position to be in thermal contact with the electricalcomponent(s), the compliant device being in an expanded state in thissecond position of the piston. The piston can be moved or caused to moveby the compliant device transitioning from its compressed state to itsexpanded state. In one example, the interfaces between theabove-discussed components are all metal. Thus, the heat transferdevice, positioned in the counterbore (or against a surface of theheatsink) and in the expanded state, can provide all-metal thermalconductive path between the electrical component(s) and the heatsink.The heat transfer device can further absorb assembly tolerances of theelectrical components, such that a typical gap filler or other filler isnot needed.

In one example, the heat transfer device can comprise a cup disposedwithin the counterbore of the heatsink, or the cup may be biased orotherwise coupled to a surface of the heatsink. The cup can furtherdefine a cavity, and can be operative to receive the piston and tofacilitate its movement therein. The piston, cup, heatsink, and flowablematerial can each comprise a type of metal, such that an all-metalthermally conductive path is created from the electrical component(s),through the heat transfer device, and out through the heatsink.

A system for thermally coupling at least one electrical component to aheatsink and absorbing assembly tolerances, in accordance with oneexample, can comprise an electronics assembly having a substrate (e.g.,a Printed Wire Board or PWB) having a plurality of electrical componentsattached thereto. A heatsink can have a plurality of counterbores, eachdefining a cavity. A plurality of heat transfer devices can be coupledto or otherwise operative with the heatsink. For instance, each heattransfer device can be positioned in a respective counterbore of theheatsink, or the cup may be biased or otherwise coupled to a surface ofthe heatsink. Each heat transfer device can comprise a variety ofcomponents and features described herein.

The present disclosure further provides a method for effecting heattransfer within an electronics device by providing an expanding thermalgap fill heat transfer device that thermally couples a heatsink to atleast one electrical component and absorbs assembly tolerances, inaccordance with one example. The method can comprise providing aheatsink having a counterbore defining a cavity, or providing a heatsink having a heat transfer surface. The method can also comprisedisposing a compliant device and a piston within the counterbore, andproviding a flowable material to be in contact with the piston and theheatsink. The method can further comprise applying a force to displacethe piston and cause the compliant device to enter a compressed state.The method can still further comprise reflowing the flowable material ina first sequence to secure the piston in a first position. The methodcan still further comprise removing the applied force and reflowing theflowable material in a second sequence to secure the piston in a secondposition to be in thermal contact with the electrical component(s).

The above method steps can be repeated to create a plurality of separateheat transfer points along the electronics assembly and heatsink, suchthat a plurality of pistons facilitate heat transfer from a plurality ofelectrical components through the heatsink. The method can compriserepeating some or all of the method steps above in multiple sequences,and positioning a plurality of electrical components adjacent aplurality of compressed heat transfer devices. The method can compriseabsorbing assembly tolerances when the plurality of pistons is incontact with the plurality of electrical components upon reflowing theheat transfer devices to be in their expanded states.

FIGS. 1A-2 show an example system 10 for thermally coupling anelectrical component to a heatsink (see FIG. 2 for an exploded view).The system 10 can comprise an electrical component 12 as part of anelectronics assembly 14. The electrical component 12 can be positionedabout or in close proximity to a heatsink 16 operative to transfer heatfrom the electronic component 12 about a path (e.g., path P1). Theheatsink 16 can have a counterbore 18 defining a cavity 20 (throughoutthis application, cavities and voids will be shown having “air bubbles”to avoid illustrating numerous cross sectional lines on all thecomponents in the cross-sectional views). The system can comprise a heattransfer device 22 positionable in the counterbore 18. In some aspects,the system 10 can further comprise a cup 24 disposed within thecounterbore 18 of the heatsink 16, the cup defining a cavity (e.g., seecavity 26 in FIG. 2). The cup 24 can be operative to receive a piston 25to facilitate its movement therein (see arrows A and B) during reflowingstages or processes.

A compliant device 28, such as an elastomeric disk or cylinder, can bepositioned between the cup 24 and the piston 25. The compliant device 28can be caused to move to and from a compressed state C1 (FIG. 1A) and toan expanded state X1 (FIG. 1B) to facilitate movement of the piston 25.A flowable material 30 can be disposed about the piston 25 (and can bedisposed on other surfaces of the various components of the system, suchas between and/or on the cup 24 or the counterbore 18 (e.g., see FIG.2)). The flowable material 30, such as solder, can comprise a lowermelting point than the piston 25 and the heatsink 16 in order toproperly reflow the flowable material 30 without damaging the piston 25,the heatsink 16 or any of the electronics of the system. In one aspect,the piston 25 can be made of copper, and the heatsink 16 can be made ofaluminum. However, those skilled in the art will recognize that othermaterials can be used and that are suitable to perform as intended. Theflowable material 30 discussed herein can comprise other materials, suchas lead, tin, silver, and the like, as long as its melting pointtemperature is less than the surrounding components.

The flowable material 30 can be configured to be capable oftransitioning between a solid and liquid state upon the application ofenergy, such as heat (e.g., reflowing solder). The flowable material 30can assist with securing the piston 25 in a desired position while inthe solid state and moving the piston 25 while in the liquid state, asfurther discussed below. For example, in FIG. 1A the piston 25 is shownas being held in a first position by the flowable material 30 being inthe solid state with the compliant device 28 in its compressed state C1,wherein in this state the compliant device 28 applies a biasing forceagainst or to the piston 25 in an expansion direction of the compliantdevice 28. This state can be achieved by applying a sufficient force Fon the piston downward toward the compliant device 28 to compress thecompliant device 28 while reflowing the flowable material (preferablebefore the electronic component 12 is positioned adjacent the heattransfer device, which method will be discussed further below), suchthat the piston 25 is held in place in this first position via theflowable material 30 upon reaching its solidified state. With theelectronic component 12 in position adjacent the heat transfer device22, the flowable material 30 can again be reflowed, such that thecompliant device 28 is caused to expand, thereby moving the piston 25into a second position (FIG. 1B) to be in thermal contact with theelectrical component 12. Consequently, the compliant device 28 wouldthen be in its expanded state E1. Upon such movement of the piston 25, atolerance distance D1 between the piston 25 and the electrical component12 can be accounted for as the piston 25 moves from its first position(FIG. 1A) to its second position (FIG. 1B).

It is not uncommon for the electrical components of the electronicsassembly to comprise differing tolerances, such as between theelectrical component and the heatsink. One particular advantage of thepresent invention is the ability to account for and operate with suchdiffering tolerances. Indeed, the amount of expansion of the compliantdevice, and coincidently the distance that the piston is caused orpermitted to move or travel in order to come into thermal contact withan electrical component, may be different from one heat transfer deviceto another and from electrical component to another within the sameelectronics assembly. Stated differently, a plurality of heat transferdevices can be configured to operate independent of one another and canbe caused to make thermal contact with a plurality of electricalcomponents irrespective of differing tolerances between the electricalcomponents and the heatsink.

In FIG. 1B the compliant device 28 is shown in its expanded state E1 andthe flowable material 30 is in its solid state as mechanically coupledto the electronics component and the heatsink. It will be understoodthat “expanded” can mean that the compliant device 28 is in at least apartially expanded state (transferring at least some or all of itspotential energy to the piston). Indeed, “expanded” may mean thecompliant device is partially expanded when the piston makes itsanticipated thermal connection with the electrical component, or it maymean that the compliant device is fully expanded when the piston makesits anticipated thermal connection with the electrical component. In anyevent, this can be achieved during a reflowing process by allowing theflowable material to cool after the compliant device 28 has moved thepiston 25 into its second position. In this position, the piston 25 canbe secured to the electrical component 12, the cup 24, and the heatsink16. In an example where the piston, cup, heatsink, and flowable materialare each comprised of a type of metal, an all-metal thermal conductivepath P1 can be created between the electrical component 12 and theheatsink 16. As such, gap fillers for use in electronics assemblies canbe eliminated. Therefore, an advantage of this arrangement is thecreation of a gap free solid metal interface independent of mechanicalassembly tolerances, and that the thermal conductivity of the interfacecan be increased by several orders of magnitude. For example, in thecase of solder being used as the flowable material, the metal interfacehas the thermal conductivity of solder (30 W/m-K) that is an order ofmagnitude higher than that of a gap filler (2.8 W/m-K). Similar resultscan be achieved with other types of flowable materials.

FIG. 2 illustrates an exploded view of the system 10 of FIGS. 1A and 1B,in accordance with one example. As shown, the electronics assembly 14comprises an attached electrical component 12. An example electronicsassembly can comprise a Printed Wiring Board (PWB) having a plurality ofelectrical chips attached thereto that require heat transfer for normaloperation (such as shown in FIG. 3). The heatsink 16 can be awater-cooled or an air-cooled aluminum coldplate; however, other knownheatsinks and/or heat transfer systems could be used.

In one aspect, the heat transfer devices discussed herein can beutilized at specific or discrete areas or locations of an electronicssystem or assembly and heatsink arrangement. As such, it is contemplatedthat an electronics system or assembly and heatsink arrangement cancomprise one or a plurality of such heat transfer devices. Of course,the electronics assembly and heatsink arrangement can be much largerthan shown (such as a relatively large PWB board with dozens or hundredsof chips attached thereto). Of course, the heatsink in such electronicsassembly could be much larger than shown in the Figures. As such, inanother aspect, a plurality of heat transfer devices as discussed hereincould be used at various locations.

As represented by the wavy lines on FIG. 2, the flowable material 30 canbe disposed on some or all of the surfaces of the counterbore 18, thecup 24, the piston 25, and/or the electrical component 12 (whether inliquid or solid state depending on the state of the heat transfer deviceand processes). The flowable material 30 can be derived from soldersheets cut to a cylindrical shape to be disposed around the piston 25,for example. A solder disk can be positioned between the piston 25 andthe compliant device 28 to secure the compliant device 28 to the piston25 to assist with smooth translation of the piston 25 during the reflowprocesses.

FIG. 3 shows a cross-sectional view of a system 40 comprising anelectronics assembly 42 having a substrate 44 having attached aplurality of electrical components 46, according to one example. Thesystem 40 is shown in an expanded state with the pistons in contact withthe electrical components 46. As shown, the system 40 can comprise aheatsink 48 operative to transfer heat from the electrical components46. The system 40 can comprise a plurality of heat transfer devices 50coupled to or otherwise operative with the heatsink 48. The heattransfer devices 50 can each be operative within a respectivecounterbore 52. Alternatively, the heat transfer devices 50 can bebiased to or otherwise coupled to a planar surface or other surface ofthe heatsink 48, as illustrated by dashed line P where the tworight-side devices 50 are coupled to a surface P of the heatsink 48. Inthe example of FIG. 3, the heat transfer devices 50 are shown as beingsimilar to the expanded devices shown in FIG. 1B. However, anycombination of components of the heat transfer devices 50 discussedherein can be used with the example system of FIG. 3.

In one example of manufacturing the system 40, a method of thermallycoupling the heatsink 48 to one (of possibly many) electrical components46 comprises providing the heatsink 48 having a counterbore 52 defininga cavity 54 (e.g., FIG. 2). The method can comprise disposing acompliant device 55 and a piston 56 within the counterbore 52. Themethod can comprise providing a flowable material (see e.g., FIG. 1B)disposed about the piston 56 and/or the heatsink 48. The method cancomprise applying a force (e.g., force F in FIG. 1A) to displace thepiston 56 and cause the compliant device 55 to enter a compressed state(e.g., FIG. 1A). The method can comprise reflowing the flowable material(not shown here) in a first sequence to secure the piston 56 in a firstposition (e.g., FIGS. 1A, 4, 5, and 6A). Reflowing can be achieved byapplying energy, such as heat, to the flowable material sufficient toplace it in a liquid state, and then allowing it to cool to a solidstate, thereby securing the piston in the first position, for example.The method can comprise removing the applied force from the piston 56(or alternatively inserting a pre-loaded or pre-compressed heat transferdevice into a counterbore) and reflowing the flowable material in asecond sequence, thereby allowing the compliant device 55 to release itspotential energy and move the piston 56 against the electrical device46. The flowable material can be allowed to cool and solidify, therebysecuring the piston 56, in a second position relative to the heatsink 48and the electrical component 46. The piston 56, therefore, can be causedto be in thermal contact with the electrical component 46 and theheatsink 48, thereby providing a thermal path P3 (dashed lines), drawingheat from the electrical component 46, through the heat transfer device50 and to the heatsink 48. In some examples, the method can compriseproviding a metal cup 60 within the counterbore 52 of the heatsink 48(see FIG. 4 for an example heat transfer device without a cup).

Alternatively, a heat transfer device can be manufactured (e.g.,pre-loaded or pre-compressed) and then later inserted into a counterbore of a heatsink for subsequent expansion and thermal interaction withan electrical component of an electronics assembly. For instance, at aseparate location the compliant device 55 and the piston 56 can beinserted into the cup 60, whereby solder is disposed about thecomponents. A force can then be applied against the piston 56 tocompress the compliant device 55, and the solder reflowed in a firstsequence and then allowed to cool, thereby placing the piston 56 of theheat transfer device 50 in a pre-loaded or pre-compressed firstposition. The heat transfer device can then be later inserted into ordisposed within a counterbore of the heatsink.

In some examples, the method can further comprise concurrently (orsequentially) inserting a plurality of heat transfer devices into aplurality of respective counterbores (or elsewhere on a heatsink). Thiscan be achieved as discussed above, either by a plurality of individualheat transfer device components inserted into the counterbores, or by aplurality of compressed heat transfer devices loaded into thecounterbores in the compressed state.

The method can comprise positioning a plurality of electrical components46 adjacent the plurality of heat transfer devices 50 while thecompliant devices 55 are in their compressed state. The electronicsassembly 42 can be made to be operative with the heatsink at this time,or later. The method can comprise reflowing the flowable material in asecond sequence, thereby allowing the compliant devices 55 to releasetheir potential energy and move their respective pistons 56 againsttheir respective electrical components 46. The flowable material isallowed to cool and solidify, thereby securing the pistons 56 to the cup60, the heatsink 48, and the electrical components 46. In this position,the pistons 56, therefore, can be caused to be in thermal contact withtheir respective electrical components 46 and the heatsink 48.

The devices, systems and methods described herein can provide aplurality of separate metal-to-metal heat transfer points or areas Hbetween the heat transfer devices and the electrical components. Theseheat transfer points H can each include a substantially smaller area orfoot-print of heat transfer surface areas as compared to existingsystems that use thermal gap fillers, which can consume much or all ofthe available surface area of the PWB. Moreover, the devices, systemsand methods described herein can function to absorb or account forassembly tolerances of the plurality of mounted electrical components.To this end, when a plurality of chips, for instance, are manufacturedon a PWB, there exists a variety of tolerance differences in the chipsrelative to other chips, the PWB and/or the heatsink (e.g., tolerancegaps and differences in the x, y, and/or z directions). Therefore, oneadvantage of the present technology discussed herein is the ability ofthe heat transfer devices to account for inconsistent or differenttolerances. For instance, when reflowing the heat transfer devices 50 inthe second sequence, a particular piston 56 can come to rest in itssecond state at a different height and/or position relative to otherpistons of other heat transfer devices due to the tolerance differencesin the electronics assembly. As such, the method can further compriseconfiguring the plurality of heat transfer devices to operateindependent of one another, such that the plurality of heat transferdevices make thermal contact with the plurality of electrical componentson the substrate irrespective of differing tolerances between theelectrical components and the heatsink.

FIG. 4 illustrates a cross-sectional view of a system 70 for thermallycoupling one or more (in this case three) electrical components 72 to aheatsink 74, in accordance with an example. The system 70 can comprisethe electrical components 72 as part of an electronics assembly 78(e.g., FIG. 3). It is contemplated that a single heat transfer devicecan be caused to thermally couple to a plurality of electricalcomponents in accordance with any of the examples discussed herein, asexemplified in FIG. 4. The electrical components 72 can be positionednear the heatsink 74 and can be operative to transfer heat from theelectronics assembly 78. The heatsink 74 can have a counterbore 80defining a cavity 82 and operative to receive a piston 84 and tofacilitate its movement therein. The system 70 can comprise a heattransfer device 86 positionable in the counterbore 80. As compared tothe device of FIG. 1A, this system 70 and heat transfer device 86 isdevoid of a cup. While FIG. 4 only shows an example heat transfer device86 in a compressed state C4, it will be appreciated that it can functionsimilar to the example heat transfer devices and methods discussed abovein relation to FIGS. 1-3, as well and others as contemplated herein.Here, a compliant device 88, such as an elastomeric material, can bepositioned between the heatsink 74 and the piston 84. The compliantdevice 88 can be movable from a compressed state C4 to an expanded state(not shown) to facilitate movement of the piston 84. A flowable material89 can be disposed about the piston 84 and/or the counterbore 80. Themethod of manufacture and operation of the example of FIG. 4 will not bediscussed in great detail because the reflow processes and pistonmovements are similar to that of FIGS. 1-3 and others. The primarydifference here is that the FIG. 4 device is devoid of a cup. However,it will continue to be appreciated that, when the piston 84 is directlysecured to the heatsink 74 via the flowable material 89 in its solidstate, an all-metal heat transfer path can be created from theelectrical components 72 through the piston 84 and to the heatsink 74.

FIG. 5 illustrates a cross-sectional view of a system 90 for thermallycoupling an electrical component to a heatsink, according to oneexample. The system 90 can comprise an electrical component 92 as partof an electronics assembly 94 (e.g., FIG. 3). The electrical component92 can be positioned near a heatsink 96 and operative to transfer heatfrom the electronics assembly 94. The heatsink 96 can have a counterbore98 defining a cavity 100. It should be appreciated that the counterbore98 and the cavity 100 would typically be formed in the heatsink as asingle counterbore defining a space in the heatsink. The system cancomprise a heat transfer device 102 positionable in the counterbore 98.The heat transfer device 102 can comprise a cup 104 disposed within thecounterbore 98 of the heatsink 96. The cup 104 can define a cavity 106.The heat transfer device 102 can comprise a piston 108 moveable withinthe cavity 106 of the cup 104. In this example, a compliant device 110can comprise a coil spring positioned between the cup 104 and the piston108 (similar to FIG. 1A). The coil spring 110 can be movable from acompressed state C5 (FIG. 5) to an expanded state (not shown) tofacilitate movement of the piston 108 during reflow. A flowable material112 can be disposed about the piston 108, the cup 104, and/or thecounterbore 98. The method of manufacture and operation of the exampleof FIG. 5 will not be discussed in great detail as these are similar tothat of FIGS. 1-3 and others. The primary difference here is that theFIG. 5 device includes at least one coil spring as the compliant device110.

FIGS. 6A and 6B show cross-sectional views of a system 120 for thermallycoupling an electrical component to a heatsink, according to anotherexample. The system 120 can comprise an electrical component 122 as partof an electronics assembly 124 (e.g., FIG. 3). The electrical component122 can be positioned near a heatsink 126 and operative to transfer heatfrom the electrical component 122. The heatsink 126 can have acounterbore 128 defining a cavity 130. The system can comprise a heattransfer device 132 positionable in the counterbore 128. The heattransfer device 132 can comprise a guide cup 134 disposed within thecounterbore 128 of the heatsink 126. The guide cup 134 can define acavity 136 and can comprise a post 138 extending from a center area ofthe guide cup 134. A piston 139 can comprise a hole 140 extendingpartially therethrough from a first surface towards a second surfacealong a central or longitudinal axis of the piston 139. The hole 140 canbe sized and configured to receive therein the post 138 of the guide cup134, such that the piston 139 can translate bi-directionally about thepost 138. The piston 139 can further comprise an upper flanged portion142 that is positionable against the electrical component 122. Acompliant device 144 can comprise a hole through its central axis (e.g.,the compliant device 144 can comprise an elastomer O-ring) and can bepositioned between the piston 139 and the cup 134, such that the post ofthe cup 134 extends through the hole of the compliant device 144. Inother words, the compliant device 144 can be disposed within the cup 134and can be circumferentially located about the post 138. The compliantdevice 144 and the piston 138 can be collectively received on the post138 for movement or expansion about the post 138.

Similar to the description with reference to FIGS. 1-3 and others, thecompliant device 144 is placed in a compressed state C6 (FIG. 6A) then aflowable material 146 is reflowed, thereby securing the piston 139 in afirst position (FIG. 6A). With the electrical component 122 in positionadjacent the piston 139 (with a tolerance distance D6), the flowablematerial can be reflowed. Upon reflowing the flowable material, thecompliant device 144 is allowed to release its potential energy to anexpanded state E6, thereby displacing the piston 139 against theelectrical component 122. Once the flowable material 146 is allowed tocool to its solid state, the piston 139 can be secured to the guide cup134 (and its post 138) and the electrical component 122, which cancreate an all-metal thermally conductive path P6 (dashed lines). Theinclusion of the guide post 138 in this example provides an additionalsurface area (i.e., the circumference area of the post) to transfer heatalong an additional path via the piston 139, among other benefits.

FIG. 7 shows an exploded view of a system 150 according to still anotherexample. The system 150 can comprise an electrical component 152 as partof an electronics assembly 154 (e.g., FIG. 3). The electrical component152 can be positioned near a heatsink 156 and operative to transfer heatfrom the electronics assembly 154. The heatsink 156 can have acounterbore 158 defining a cavity 160. The system can comprise a heattransfer device 162 positionable in the counterbore 158. The heattransfer device 162 can comprise a cup 164 disposed within thecounterbore 158 of the heatsink 156. The heat transfer device 162 cancomprise a piston 166 having a flanged portion 168 around an end of thepiston 166. The cup 164 can define a cavity 170 and can be operative toreceive a portion of the piston 166 and to facilitate its movementtherein. A compliant device 172 can be positioned between an upper areaof the cup 164 and a lower area of the flanged portion 168 of the piston166. The compliant device 172 can comprise a ring spring devicecomprising a pair of rings, and one or both rings can be configured tostore potential energy upon a given force (much like a coil spring). Thecompliant device 172 can be movable from a compressed state to anexpanded state to facilitate movement of the piston 166 during reflowingof the flowable material.

A flowable material 174, such as solder, can be disposed about thepiston 166 and/or the cup 164. The flowable material 174 has a lowermelting point than the piston 166 and the heatsink 156. The flowablematerial 174 is capable of transitioning between a solid and liquidstate upon the application of energy, such as heat. Similar to thedescription of FIGS. 1-3, the piston 166 can be held in a first positionby the flowable material 174 being in the solid state with the compliantdevice 172 in the compressed state. The flowable material 174 can bereflowed by the application of heat, for example, sufficient to melt theflowable material 174. Upon reflowing of the flowable material 174, thepiston 166 can be moveable into a second position by expansion of thecompliant device 172, such that the piston 166 is caused to be inthermal contact with the electrical component 152 upon reflowing theflowable material 174.

It is to be understood that the examples of the invention disclosed arenot limited to the particular structures, process steps, or materialsdisclosed herein, but are extended to equivalents thereof as would berecognized by those ordinarily skilled in the relevant arts. It shouldalso be understood that terminology employed herein is used for thepurpose of describing particular examples only, and is not intended tobe limiting.

Various examples of the present invention can be referred to hereinalong with alternatives for the various components thereof. It isunderstood that such examples and alternatives are not to be construedas de facto equivalents of one another, but are to be considered asseparate and autonomous representations of the present invention.

Furthermore, the described features, structures, or characteristics canbe combined in any suitable manner in one or more examples. In thedescription, numerous specific details are provided, such as examples oflengths, widths, shapes, etc., to provide a thorough understanding ofexamples discussed. One skilled in the relevant art will recognize,however, that the invention can be practiced without one or more of thespecific details, or with other methods, components, materials, etc. Inother instances, well-known structures, materials, or operations are notshown or described in detail to avoid obscuring aspects of theinvention.

While the foregoing examples are illustrative of the principles of thepresent invention in one or more particular applications, it will beapparent to those of ordinary skill in the art that numerousmodifications in form, usage and details of implementation can be madewithout the exercise of inventive faculty, and without departing fromthe principles and concepts of the invention. Accordingly, it is notintended that the invention be limited, except as by the claims setforth below.

What is claimed is:
 1. A system for effecting heat transfer within anelectronics assembly, the system, comprising: at least one electricalcomponent as part of the electronics assembly; a heatsink operative totransfer heat from the electronics assembly; an expandable heat transferdevice positioned in a cavity of the heatsink, the expandable heattransfer device comprising: a cup disposed within the cavity of theheatsink, the cup defining a cup cavity; a piston positioned at leastpartially in the cup cavity, and moveable toward the at least oneelectrical component; a flowable material disposed about the piston, theflowable material having a lower melting point than the piston and theheatsink, the flowable material transitioning between a solid state anda liquid state upon the application of energy; and a compliant devicepositioned in the cup cavity and biased against the piston, thecompliant device movable from a compressed state to an expanded state tofacilitate movement of the piston, wherein the piston is held in a firstposition by the flowable material being in the solid state with thecompliant device in the compressed state, and wherein the piston ismoveable to a second position toward the at least one electricalcomponent to be in thermal contact with the electrical component uponreflowing the flowable material in the liquid state and the compliantdevice extending to its expanded state, such that the piston transfersheat from the at least one electrical component to the heatsink.
 2. Thesystem of claim 1, wherein the piston, the heatsink, and the flowablematerial are each comprised of a type of metal, wherein an all-metalthermal conductive path is created between the at least one electricalcomponent and the heatsink through the heat transfer device.
 3. Thesystem of claim 1, wherein the cavity is defined by a counterbore,wherein a substrate supporting the at least one electrical component isbiased against the heatsink, such that at least a portion of the atleast one electrical component is positioned within the counterbore andagainst the piston.
 4. The system of claim 1, wherein the compliantdevice comprises an elastomeric material or a coil spring.
 5. The systemof claim 1, wherein the flowable material is disposed between the cupand the heatsink, and between the cup and the piston to maintain anall-metal thermal conductive path between the at least one electricalcomponent and the heatsink.
 6. The system of claim 1, wherein the cupcomprises a post and the piston comprises a hole for facilitatingtranslation of the piston about the post, and wherein the compliantdevice is configured to be disposed circumferentially about the post. 7.The system of claim 1, wherein the compliant device comprises a springpositioned against an upper surface of the cup, the spring biasing thepiston toward the at least one electrical component.
 8. An assemblycomprising a plurality of the expandable heat transfer devices,including the expandable heat transfer device, of claim 1, each heattransfer device of the plurality of expandable heat transfer devicesbeing positionable in a respective cavity of a plurality of cavitiesformed in the heatsink.
 9. The assembly of claim 8, further comprising aplurality of the electrical components, including the at least oneelectrical component, of claim 1 being part of the electronics assembly,wherein at least one of the plurality of electrical components is inthermal contact with one of the plurality of heat transfer devices. 10.An electronics assembly comprising: a substrate in support of aplurality of electrical components; a metal heatsink comprising aplurality of cavities and operative to transfer heat from the pluralityof electrical components; a plurality of heat transfer devices, eachcomprising: a cup coupled to the heatsink and disposed in one of thecavities of the heatsink, the cup defining a cup cavity; a metal pistonand a compliant device both positioned at least partially within the cupcavity of the cup, the compliant device having an expanded stateoperative to bias the piston against a representative one of theelectrical components; an amount of solder operative to secure thepiston to the representative one of the electrical components and to theheatsink, such that an all-metal thermal conductive path is formed fromthe representative one of the electrical components through acorresponding one of the heat transfer devices to the heatsink, whereinthe plurality of heat transfer devices make thermal contact with theplurality of electrical components on the substrate irrespective ofdiffering tolerances between the electrical components and the heatsink.11. The assembly of claim 10, wherein each of the heat transfer devicesis secured to one of the plurality of cavities upon reflowing the amountof solder.
 12. The assembly of claim 10, wherein each cavity comprises acounterbore, wherein the substrate is biased against the heatsink, suchthat at least a portion of the representative one electrical componentis positioned within the counterbore and against the representativepiston.
 13. The assembly of claim 12, wherein the compliant devicecomprises an elastomeric material or a coil spring.
 14. The assembly ofclaim 10, wherein the cup comprises a post and the piston comprises ahole for facilitating translation of the piston about the post, andwherein the compliant device is configured to be disposedcircumferentially about the post.
 15. A method for effecting heattransfer within an electronics assembly, the method comprising:providing a heatsink operative with the electronics assembly having atleast one electrical component supported thereon; forming a counterborein the heatsink defining a cavity, wherein a substrate supporting the atleast one electrical component is biased against the heatsink, such thatat least a portion of the at least one electrical component ispositioned within the counterbore and against the piston; positioning acompliant device and a piston of a heat transfer device into a cup, andpositioning the cup within the cavity of the heatsink; providing aflowable material to be in contact with the piston and the heatsink;applying a force to displace the piston and cause the compliant deviceto enter a compressed state; reflowing the flowable material in a firstsequence to secure the piston in a first position; and reflowing theflowable material in a second sequence to secure the piston in a secondposition in thermal contact with the at least one electrical component,the compliant member biasing the piston into the second position. 16.The method of claim 15, wherein the reflowing of the flowable materialin the second sequence further comprises heating the flowable materialto a liquid state for an amount of time sufficient to cause thecompliant device to expand and displace the piston.
 17. The method ofclaim 15, wherein the electronics assembly comprises a plurality ofelectrical components including the at least one electrical component,and wherein the method further comprises providing a plurality of heattransfer devices, including the heat transfer device, to create aplurality of separate heat transfer points along the heatsink from theplurality of electrical components.
 18. The method of claim 17, furthercomprising configuring the plurality of heat transfer devices to operateindependent of one another, such that the plurality of heat transferdevices make thermal contact with the plurality of electricalcomponents, respectively, on the electronics assembly irrespective ofdiffering tolerances between the electrical components and the heatsink.